1. Field of the Invention
The present invention pertains to pumps which employ a diaphragm.
2. Related Art and Other Considerations
Diaphragm-type pumps typically comprise a pumping chamber defined by a diaphragm and a relatively rigid or stationary housing or enclosure in which the diaphragm is mounted. Fluid acted upon by the diaphragm is admitted into the pumping chamber through an inlet valve and exits the pumping chamber via an outlet valve. Although a central portion of the diaphragm moves in the pumping chamber, the diaphragm is clasped essentially entirely around its edge or periphery by the housing and usually retained in the stationary housing by some sort of flexible yet fluid-tight seal. Various means for clasping the diaphragm in the housing have been used, such as (for example) gaskets, O-rings, and adhesives.
Examples of pumps with an edge-clamped piezoelectric diaphragm are shown in PCT Patent Application PCT/US01/28947, filed 14 Sep. 2001; U.S. patent application Ser. No. 10/380,547, filed Mar. 17, 2003, entitled “Piezoelectric Actuator and Pump Using Same”; U.S. patent application Ser. No. 10/380,589, filed Mar. 17, 2003, entitled “Piezoelectric Actuator and Pump Using Same”, all of which are incorporated herein by reference.
In such pumps, whether utilizing piezoelectric or other types of diaphragms, the seal allows at least a central portion of the diaphragm to move laterally, while holding the periphery of the diaphragm somewhat rigidly longitudinally. The rigid mounting of the edge of diaphragm by the housing has an undesirable side effect of constricting the pumping motion performed by the diaphragm. It is estimated that some current pump designs with edge-engagement of the diaphragm constrict the motion of the diaphragm by as much as 30% to 50%, thereby limiting volumetric displacement per pump stroke.
What is needed, and an object of the present invention, is apparatus, method, and/or technique for operating a diaphragm pump without the undue constriction of the diaphragm.